Tooth decay and dental disease can be caused by bacterial action resulting from the formation of plaque about the teeth and/or the entrapment of food particles between the teeth and interstices therebetween. The removal of plaque and entrapped food particles reduces the incidence of caries, gingivitis, and mouth odors as well as generally improving oral hygiene. Conventional brushing has been found to be inadequate for removing all entrapped food particles and plaque. To supplement brushing, dental flosses and tapes have been recommended. The term "dental floss", as used herein, is defined to include both dental flosses, dental tapes and any similar article.
To improve the effectiveness and convenience of dental flosses, dental flosses combining a thin "floss" portion and a thickened "brush" portion, together with a threader have been developed. The brush portion, when drawn between tooth surfaces, has been found to provide an improved cleaning action which removes materials left by the floss portion, when used alone. The combination provides a substantially superior cleaning action. Such a device is described in U.S. Pat. No. 4,008,727, for example. The complexity of this product requires that each floss segment be individually manufactured and that the product be packaged as bundles of the individual, separate floss articles.
A continuous yarn having brush segments separated by thinner segments is disclosed in U.S. Pat. Nos. 4,008,727 and 4,142,538. However, products formed using conventional textured nylon yarns and previously developed manufacturing processes were not satisfactory. Manufacture of brush floss products of this type involves applying a polymer solution to the yarn. The solvent is then selectively evaporated from the thinned segment portion while avoiding solvent evaporation from the brush portion, the yarn being maintained under high tension during this procedure. The solvent in the brush portion is then removed while the yarn is relaxed, that is, under low or no tension. Thin yarn products of most texturizing processes were found to be too weak to be placed under the high tension required for forming the desired thin section. Furthermore, the polymer impregnated brush portion did not regain its original bulk and texture when the tension was relaxed prior to solvent removal from the brush portion.
An improved floss brush product and processes for manufacturing it which overcome these deficiencies are described in U.S. Pat. No. 5,284,169. The entire contents of the above application is hereby incorporated by reference.
In manufacturing these continuous floss brushes, measurement of actual floss length and/or number of floss units for packaging presents a difficult problem because the brush portion is highly expanded and stretches when placed under any tension. Therefore, the lengths of floss segments may differ depending upon the tension under which they are measured and the amount of expansion or bulking during manufacture. The segment lengths are thus not precisely reproducible, and accordingly, traditional methods for automatically measuring length and/or number of use segments based directly or indirectly on length measurements are not effective with this product. For the same reason, locating of suitable points to cut lengths of floss for packaging and use based on length presents a problem.